Resumen de Songbirds really do fly south for the winter
Most songbirds in the Americas, including those that do not migrate, live in the South American tropics, and almost every migratory bird species has close relatives in the tropics. Now Ben Winger of the University of Chicago and his colleagues have strong evidence that most migrants hail from the north, not the south. They found that long-distance migration was twice as likely to arise in temperate ancestors as tropical ones.
